In vitro evaluation of three-dimensional single-walled carbon nanotube composites for bone tissue engineering.

The purpose of this study was to develop three-dimensional single-walled carbon nanotube composites (SWCNT/PLAGA) using 10-mg single-walled carbon nanotubes (SWCNT) for bone regeneration and to determine the mechanical strength of the composites, and to evaluate the interaction of MC3T3-E1 cells via cell adhesion, growth, survival, proliferation, and gene expression. PLAGA (polylactic-co-glycolic acid) and SWCNT/PLAGA microspheres and composites were fabricated, characterized, and mechanical testing was performed. MC3T3-E1 cells were seeded and cell adhesion/morphology, growth/survival, proliferation, and gene expression analysis were performed to evaluate biocompatibility. Imaging studies demonstrated microspheres with uniform shape and smooth surfaces, and uniform incorporation of SWCNT into PLAGA matrix. The microspheres bonded in a random packing manner while maintaining spacing, thus resembling trabeculae of cancellous bone. Addition of SWCNT led to greater compressive modulus and ultimate compressive strength. Imaging studies revealed that MC3T3-E1 cells adhered, grew/survived, and exhibited normal, nonstressed morphology on the composites. SWCNT/PLAGA composites exhibited higher cell proliferation rate and gene expression compared with PLAGA. These results demonstrate the potential of SWCNT/PLAGA composites for musculoskeletal regeneration, for bone tissue engineering, and are promising for orthopedic applications as they possess the combined effect of increased mechanical strength, cell proliferation, and gene expression.

Short interfering RNA against transient receptor potential vanilloid 1 attenuates cisplatin-induced hearing loss in the rat.

Cisplatin, a chemotherapeutic agent of choice for the treatment of solid tumors, produces hearing loss in approximately half a million new cancer patients annually in the United States. The hearing loss is due, in part, to increased generation of reactive oxygen species (ROS) in the cochlea, leading to lipid peroxidation and damage or death of outer hair cells in the organ of Corti. The cochlea expresses the transient receptor potential vanilloid 1 (TRPV1), which are normally expressed on small diameter neurons in the peripheral nervous system and mediate thermal sensitivity, but whose role in the cochlea is unclear. In this study, we show that TRPV1 is coregulated along with the NADPH oxidase isoform, NOX3, by cisplatin. Induction of these proteins by cisplatin is dependent on ROS generation, since it is reversed by systemic lipoic acid administration. In organ of Corti hair cell cultures (UB/OC-1 cells), cisplatin activates and induces TRPV1 and NOX3, leading to apoptosis of these cells. Inhibition of TRPV1 by capsazepine or ruthenium red reduced the apoptosis, implicating TRPV1 in this process. Treatment of UB/OC-1 cultures with short interfering RNA (siRNA) against either TRPV1 or NOX3 reduced cisplatin-induced apoptosis, while round window application of TRPV1 siRNA to rats reduced TRPV1 expression, decreased damage to outer hair cells and reduced cisplatin-induced hearing loss. These data provide a link between NOX3 and TRPV1 in cisplatin-induced hearing loss and suggest that targeting these proteins for knockdown by siRNA could serve as a novel approach in treating cisplatin ototoxicity.

Ginkgo biloba extract (EGb 761) protects against cisplatin-induced ototoxicity in rats.

HYPOTHESIS: A standardized Ginkgo biloba extract, EGb 761, may have protective effect against cisplatin-induced ototoxicity in rats. BACKGROUND: Cisplatin-induced ototoxicity is a major dose-limiting side effect in anticancer chemotherapy. Cisplatin-induced ototoxicity has been correlated to depletion of the cochlear antioxidant system and increased lipid peroxidation. EGb 761 contains potent antioxidants capable of scavenging free radicals, inhibiting nitric oxide synthesis, reducing lipid peroxidation, and protecting against apoptosis. The purpose of this study was to investigate the effect of EGb 761 on cisplatin-induced ototoxicity in rats. METHODS: Male Wistar rats were divided into four groups and were treated as follows: 1) vehicle control; 2) cisplatin (13 mg/kg, intraperitoneally) plus vehicle; 3) EGb 761 (200 mg/kg, intraperitoneally); and 4) EGb 761 plus cisplatin. Auditory brainstem responses (ABRs) were measured pretreatment and 72 hours posttreatment, and threshold shifts were analyzed. Endocochlear potentials (EPs) were also obtained at 72 hours posttreatment. Cochleae were harvested and processed for scanning electron microscopy after completion of auditory testing. RESULTS: Cisplatin-treated rats showed significant ABR threshold shifts across all frequencies (click, and 2-, 4-, 8-, 16-, and 32-kHz tones) compared with each of the other groups (p < 0.001). Rats treated with EGb 761 plus cisplatin did not show significant ABR threshold shifts (p > 0.05). Similarly, the EPs of cisplatin-treated rats were decreased significantly approximately 50% in comparison with the other groups (p < 0.001). The EPs of EGb 761 plus cisplatin-treated rats were decreased less than 20% compared with vehicle control group or the EGb 761 only group (p < 0.01). The scanning electron microscopy observation indicated severe outer hair cell loss in the basal turn of cochleae of cisplatin-treated rats, whereas outer hair cells remained intact in the rats treated with EGb 761 plus cisplatin. CONCLUSION: These results demonstrate that EGb 761 protects against cisplatin-induced ototoxicity.

Mechanisms of cisplatin-induced ototoxicity and prevention.

Cisplatin is a widely used chemotherapeutic agent to treat malignant disease. Unfortunately, ototoxicity occurs in a large percentage of patients treated with higher dose regimens. In animal studies and in human temporal bone investigations, several areas of the cochlea are damaged, including outer hair cells in the basal turn, spiral ganglion cells and the stria vascularis, resulting in hearing impairment. The mechanisms appear to involve the production of reactive oxygen species (ROS), which can trigger cell death. Approaches to chemoprevention include the administration of antioxidants to protect against ROS at an early stage in the ototoxic pathways and the application of agents that act further downstream in the cell death cascade to prevent apoptosis and hearing loss. This review summarizes recent data that shed new light on the mechanisms of cisplatin ototoxicity and its prevention.

Ototoxicity: therapeutic opportunities.

Two major classes of drugs currently in clinical use can cause permanent hearing loss. Aminoglycoside antibiotics have a major role in the treatment of life-threatening infections and platinum-based chemotherapeutic agents are highly effective in the treatment of malignant disease. Both damage the hair cells of the inner ear, resulting in functional deficits. The mechanisms underlying these troublesome side effects are thought to involve the production of reactive oxygen species in the cochlea, which can trigger cell-death pathways. One strategy to protect the inner ear from ototoxicity is the administration of antioxidant drugs to provide upstream protection and block the activation of cell-death sequences. Downstream prevention involves the interruption of the cell-death cascade that has already been activated, to prevent apoptosis. Challenges and opportunities exist for appropriate drug delivery to the inner ear and for avoiding interference with the therapeutic efficacy of both categories of ototoxic drugs.

Partial protection by lipoic acid against carboplantin-induced ototoxicity in rats.

OBJECTIVE: To investigate the alterations in auditory brainstem evoked responses (ABRs) and the changes of carboplatin-induced ototoxicity in the cochlear oxidant/antioxidant systems and otoprotection by an antioxidant lipoate. METHODS: Male wistar rats were divided into four groups and treated as follows: 1) vehicle (saline) control, 2) carboplatin (256 mg/kg, i.p.), 3) lipoate (100 mg/kg, i.p.), 4) lipoate + carboplatin. Post-treatment ABRs were performed after four days and rats were sacrificed with their cochleae harvested and analyzed. RESULTS: Carboplatin significantly elevated ABR threshold above the pretreatment thresholds. Lipoate+carboplatin treated rats showed decreased elevation of hearing threshold. Carboplatin significantly depleted cochlear reduced to oxizized glutathione (GSH/GSSG) ratio, whereas lipoate+carboplatin treatment increased GSH/GSSG ratio. Carboplatin significantly decreased cochlear copper zinc-superoxide dismutase (CuZn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST) activities and enzyme protein expressions and a significant increase in Mn-SOD activity, protein expression and malondialdehyde (MDA) level. Cochlear antioxidant enzyme activities, enzyme protein expressions and MDA level were partially restored in lipoate+carboplatin treated rats, compared to carboplatin alone. CONCLUSION: Carboplatin-induced ototoxicity is related to impairment of cochlear antioxidant system and otoprotection conferred by lipoate is associated with partial sparing of the cochlear antioxidant defense system.

Time response of carboplatin-induced nephrotoxicity in rats.

Carboplatin, a second-generation platinum-containing anti-cancer drug, is currently being used against human cancers. High-dose carboplatin chemotherapy can cause renal tubular injury in cancer patients. We have shown a dose-dependent nephrotoxicity of carboplatin in a rat model. However, the time response of carboplatin-induced renal injury has not been explored. This study investigated the time response of carboplatin-induced nephrotoxicity in rat. Male Wistar rats (250-300 g) were divided into two groups of 30 animals each and treated as follows: (1) control (saline, intraperitoneally) and (2) carboplatin (256 mg kg(-1), intraperitoneally). The animals (n = 6) from each group were sacrificed 1-5 days after treatment. The blood and kidneys were isolated and analyzed. Plasma creatinine, blood urea nitrogen (BUN), and blood urea levels were increased significantly in response to carboplatin in a time-dependent manner, indicating potential nephrotoxicity. Carboplatin time-dependently increased the renal platinum concentration, renal xanthine oxidase activity, increased membrane lipid peroxidation (MDA) concentration, while ratio of reduced-to-oxidized glutathione (GSH/GSSG) depleted significantly, indicating oxidative renal injury. Renal anti-oxidant enzymes, such as cytosolic copper/zinc-superoxide dismutase (CuZn-SOD) and mitochondrial manganese (Mn)-SOD, catalase (CAT), and glutathione peroxidase (GSH-Px) activities were decreased significantly due to carboplatin 3-5 days post-treatment. The protein expressions of renal CuZn-SOD and Mn-SOD significantly depleted 3-5 days after carboplatin administration, indicating decline in de novo synthesis of enzyme proteins. The data suggested that carboplatin caused time-dependent oxidative renal injury, as evidenced by renal anti-oxidant depletion, enhanced lipid peroxidation, platinum content, plasma creatinine BUN, and blood urea levels in rats.

Protection against cisplatin ototoxicity by adenosine agonists.

Cisplatin is a commonly used antineoplastic agent that causes ototoxicity through the formation of reactive oxygen species (ROS). Previous studies have shown that cisplatin causes an upregulation of A(1) adenosine receptor (A(1)AR) in the cochlea, and that application of the adenosine agonist, R-phenylisopropyladenosine (R-PIA), to the round window (RW) results in significant increases in cochlear glutathione peroxidase and superoxide dismutase. These data suggest that adenosine receptors (ARs) are an important part of the cytoprotective system of the cochlea in response to oxidative stress. The purpose of the current study was to investigate the effect of various adenosine agonists on cisplatin ototoxicity using RW application. Auditory brainstem response (ABR) thresholds were recorded in anesthetized chinchillas at 1, 2, 4, 8 and 16kHz. The auditory bullae were surgically opened, and 1mM R-PIA, 10microM 8-cyclopentyl-1,3-dipropylxanthine (DPCPX)/R-PIA (1mM) cocktail, 100microM 2-chloro-N-cyclopentyladenosine (CCPA), 2-[4-(2-p-carboxy-ethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS) or vehicle were applied to the RW. After 90min, the remaining solution was removed and cisplatin was applied to the RW. The bullae were closed and the animals recovered for 72h, after which, follow-up ABRs were performed. Cochleae were harvested for scanning electron microscopy (SEM) and for lipid peroxides. Pre-administration of the A(1)AR agonists R-PIA or CCPA significantly reduced cisplatin-induced threshold changes at all but the highest test frequency. In addition, A(1)AR agonists protected against cisplatin-induced hair cell damage and significantly reduced cisplatin-induced lipid peroxidation. Co-administration of the A(1)AR antagonist, DPCPX, completely reversed the protective effects of R-PIA. In contrast, pretreatment with CGS-21680, an A(2A) adenosine receptor (A(2A)AR) agonist, significantly increased cisplatin-induced threshold changes. Our findings are consistent with the notion that the A(1)AR contributes significantly to cytoprotection in the cochlea, and thereby protects against hearing loss.

Vitamin E reduces cisplatin ototoxicity.

OBJECTIVES/HYPOTHESIS: Cisplatin ototoxicity is a major dose-limiting factor in the treatment of several neoplasms. Vitamin E, a slow-acting free radical scavenger, has been shown to ameliorate nephrotoxicity and endothelial cell damage in animals receiving cisplatin. The purpose of the study was to determine the effectiveness of vitamin E as an otoprotectant. STUDY DESIGN: Prospective, randomized controlled trial in the rat model. METHODS: Wistar rats (weight, 261-386 g) were sedated using 172.4 mg/kg intramuscular ketamine and 3.4 mg/kg xylazine. Baseline auditory brainstem response (ABR) testing was performed in response to clicks and 8-, 16-, and 32-kHz tone bursts. After auditory thresholds were determined, the animals received intraperitoneal drug administration according to one of three group classifications. Group 1 received 4 g/kg vitamin E followed after 30 minutes by 16 mg/kg cisplatin. Group 2 received 6 mL/kg soybean oil followed after 30 minutes by cisplatin. Group 3 received soybean oil followed after 30 minutes by 16 mL/kg saline. After 3 days' follow-up, ABR testing was performed and threshold changes were recorded. Cochleae were removed and processed for scanning electron microscopy after follow-up auditory testing was carried out. RESULTS: Group 2 animals showed marked hearing loss with average threshold shifts of 28.75 +/- 2.3 dB for clicks, 30.0 +/- 1.9 dB at 8 kHz, 21.25 +/- 4.0 dB at 16 kHz, and 45.0 +/- 4.2 dB at 32 kHz. No significant loss was observed in group 3 with shifts of 2 +/- 1.3 dB, 3 +/-3.0 dB, -2.2 +/- 3.1 dB, and -1.1 +/- 4.0 dB for clicks and tone bursts at 8, 16, and 32 kHz, respectively. Significant protection was seen in group 1 animals compared with group 2 animals. In the former group, threshold shifts of 12.5 +/- 3.1 dB for clicks, 7.5 +/- 2.5 dB at 8 kHz, 5.0 +/- 3.3 dB at 16 kHz, and 24.4 +/- 5.6 dB at 32 kHz were observed. These findings were supported by the scanning electron microscope observations that severe outer hair cell destruction occurred in group 2 rats, whereas outer hair cells were preserved to a much greater extent in the cochleae of rats in group 1 that were pretreated with vitamin E. CONCLUSION: Vitamin E appears to have a protective effect against cisplatin ototoxicity.

Noise induces A1 adenosine receptor expression in the chinchilla cochlea.

Adenosine plays a major cytoprotective role during ischemia and conditions of oxidative stress. Previous studies in our laboratory indicate that oxidative stress induces expression of the A1 adenosine receptor (A1AR) via activation of nuclear factor (NF)-kappaB. In this study, we tested whether noise exposure could induce oxidative stress and determine whether this induces expression of the A1AR in the chinchilla cochlea. Chinchillas were exposed to a 96 dB 4 kHz octave band of noise for 6 h of daily exposure, followed by an 18 h noise-free period. This noise paradigm resulted in threshold shifts of 10-60 dB over the frequency range (1-16 kHz) tested. Radioligand binding studies for the A1AR indicate a significant increase in receptor ( approximately 2-fold) expression soon after the first noise exposure period (usually within approximately 8 h of the initiation of noise), which gradually returned to basal levels by day 7. The rise in A1AR levels was followed by a significant increase in malondialdehyde levels by day 3, which also recovered by day 7. Assessment of the activity of NADPH oxidase in the cochlea indicates a significant increase in enzyme activity which was evident by approximately 8 h following initiation of noise exposure, and which persisted for at least up to day 3. Electrophoretic mobility shift assays indicate that the increase in A1AR was associated with a significant increase in NF-kappaB activity following noise exposure. We conclude that noise exposure induces A1AR expression, which might be mediated, in part, through generation of reactive oxygen species and activation of NF-kappaB.

Round window pH manipulation alters the ototoxicity of systemic cisplatin.

The effect of manipulation of pH on the ototoxicity of systemic cisplatin was studied in Wistar rats. After control auditory brainstem responses (ABR) were performed, the auditory bullae were opened and acidic (pH 6.0), neutral (pH 7.4) or basic (pH 9.0) phosphate-buffered saline (PBS) was applied to fill the round window niche (RWN). After 30 min, 13 mg/kg cisplatin solution or saline was administered intraperitoneally. After 3 days, follow-up ABRs were performed and cochleae were processed for morphological analysis. Animals that received basic PBS on the RWN and cisplatin intraperitoneally had significantly smaller ABR threshold shifts compared to rats pretreated with neutral pH buffer (P<0.05). Animals that received acidic PBS on the RWN and systemic cisplatin showed significantly greater ABR threshold shifts compared to those pretreated with neutral pH buffer (P<0.05). No significant threshold changes were observed in animals that received buffer of any pH on the RWN, followed by saline intraperitoneally. Semiquantitative analysis of hair cell survival confirmed a protective effect by basic PBS against cisplatin and a synergistic effect by acidic PBS on cisplatin ototoxicity (P<0.05). It appears that changes in cochlear pH can modulate the ototoxic effects of systemically applied cisplatin.

Aminoguanidine reduces cisplatin ototoxicity.

Cisplatin is known to cause high-frequency neurosensory hearing loss. While reactive oxygen species have been shown to play a role, reactive nitrogen species have been implicated, but not proven to be involved, in cisplatin ototoxicity. The purpose of the present study was to investigate the role of nitric oxide (*NO) in cisplatin ototoxicity by administering aminoguanidine (AG), a relatively specific inhibitor of inducible nitric oxide synthase (iNOS), in conjunction with cisplatin. Rats were injected with cisplatin, AG, or both. Auditory brainstem evoked responses (ABR) were measured before and 3 days after cisplatin administration. The cochlear tissue was then assayed for *NO and malondialdehyde. Cisplatin alone caused significant ABR threshold shifts at all stimuli tested, whereas AG alone caused no shifts. There was a significant reduction in threshold shift for clicks and 16 kHz tone bursts (but not 32 kHz) when AG was given with cisplatin. The malondialdehyde concentration (but not the *NO concentration) in the AG/cisplatin group was significantly lower than that of the cisplatin group. This suggests that AG reduces cisplatin ototoxicity by directly scavenging hydroxyl radicals. The iNOS pathway may play a role in the generation of free radicals and hearing loss resulting from cisplatin administration, but this conclusion was not supported by our data.

Carboplatin-induced oxidative injury in rat inferior colliculus.

Carboplatin is currently being used as an anticancer drug against human cancers. However, high dose of carboplatin chemotherapy resulted in ototoxicity in cancer patients. Carboplatin-induced ototoxicity was related to oxidative stress to the cochlea and inner hair cell loss in animals. It is likely that initial oxidative injury spreads throughout the neuroaxis of the auditory system later. The study aim was to evaluate carboplatin-induced hearing loss and oxidative injury to the central auditory system (inferior colliculus) of the rat. Male Wistar rats were divided into two groups of seven animals each and treated as follows: (1) control (normal saline, intraperitoneal [i.p.]) and (2) carboplatin (256 mg/kg, i.p.). Auditory brain-evoked responses (ABRs) were recorded before and 4 days after treatments. The animals were sacrificed on the 4th day and inferior colliculus from brain stem and cerebellum were isolated and analyzed. Carboplatin significantly elevated the hearing threshold shifts at clicks, 2-, 4-, 8-, 16-, and 32-kHz tone burst stimuli. Carboplatin significantly increased nitric oxide and lipid peroxidation, xanthine oxidase, and manganese superoxide dismutase activities in the inferior colliculus, but not in the cerebellum, indicating an enhanced flux of free radicals in the central auditory system. Carboplatin significantly depressed the reduced to oxidized glutathione ratio, antioxidant enzyme activities, such as copper-zinc superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, and enzyme protein expressions in the inferior colliculus, but not in the cerebellum, 4 days after treatment. The data suggest that carboplatin induced oxidative injury specifically in the inferior colliculus of the rat leading to hearing loss.

Migration of cochlear lateral wall cells.

The role of apoptosis and proliferation in maintenance of cochlear lateral wall cells was examined. The methods employed for detection of apoptosis were the Hoechst fluorescence stain and TUNEL (TdT-mediated dUTP-biotin nick-end-labeling) assay, and proliferations were 5-bromo-2'-deoxyuridine (BrdU) incorporation and presence of the proliferating cell nuclear antigen. The incidence of apoptosis in the strial marginal cell was 50% greater (32.9+/-3.7%) than strial intermediate and basal cells but similar to spiral ligament cells. Although division of marginal strial cells was rarely detected, a significant number of proliferating cells in the remaining stria vascularis and spiral ligament were observed. These data implied that replacement of marginal cells arose elsewhere and could be followed by a BrdU-deoxythymidine pulse-chase study. At 2 h post injection, nuclear BrdU in marginal cells was not detected; however, by 24 h post injection, 20-25% of marginal cell nuclei were BrdU-positive. These observations are consistent with the hypothesis that marginal cells were replaced by underlying cells. Cell migration appears to be an important mechanism for preserving the function and structure of the stria vascularis.

Influence of pH on the ototoxicity of cisplatin: a round window application study.

Cisplatin is an antineoplastic agent that produces a number of dose-limiting side effects, including ototoxicity. We investigated the effect of pH on cisplatin ototoxicity. Auditory brainstem responses (ABR) were recorded in chinchillas. Then the auditory bullae were opened and acidic (pH=6.5), neutral (pH=7.4) or alkaline (pH=10.2) phosphate-buffered saline (PBS) was applied to the round window membrane. After 30 min, any remaining solution was removed and cisplatin solution was applied to the round window membrane. After 3 days, follow-up ABRs were performed and the cochleae were processed for morphological analysis. Neutral PBS+cisplatin administration resulted in profound threshold changes at all frequencies. Acidic PBS+cisplatin administration showed had a trend of increased threshold changes, but the change did not reach statistical significance. However, the degree of hair cell loss was significantly higher than that of the neutral PBS-cisplatin group. Alkaline PBS significantly reduced cisplatin-induced threshold changes (P<0.05) compared to the neutral PBS group. Because the pH of cisplatin solution was 6.0, pH 6.0 PBS was applied to round window membrane. This acidic PBS solution did not cause any hearing impairment. These results demonstrate that pH can modulate the ototoxic effects of cisplatin.

Round window application of D-methionine provides complete cisplatin otoprotection.

OBJECTIVE: Cisplatin is a widely used, very effective chemotherapeutic agent that can cause severe ototoxicity. In this study, D-methionine was tested as an otoprotectant via round window membrane (RWM) application in the chinchilla. METHODS: A minute amount of cisplatin alone, or D-methionine followed by cisplatin, was applied topically directly to the intact RWM of anesthetized adult chinchillas. Auditory brainstem responses were measured before and 1 week after topical round window application. Animals were killed, and the cochleas were examined. RESULTS: The ears pretreated with D-methionine were completely protected from hearing loss and hair cell loss in the organ of Corti compared with controls. The ears receiving cisplatin without D-methionine protection sustained nearly complete hearing loss with threshold shifts of >60 dB, with extensive outer hair cell loss throughout the organ of Corti but particularly in the basal turn. CONCLUSION: These results demonstrate that topical D-methionine provides excellent otoprotection against cisplatin-induced ototoxicity both electrophysiologically and structurally.

Cisplatin up-regulates the adenosine A(1) receptor in the rat kidney.

Cisplatin, a widely used anticancer drug, produces significant oto- and nephrotoxicity. Previous data from our laboratory, using cultured cell lines, indicated that cisplatin increases the expression of the adenosine A(1) receptor subtype through generation of reactive oxygen species and activation of nuclear factor-kappa B (NF-kappa B). Since the adenosine A(1) receptor plays an important role in normal renal physiology, this study was performed to determine whether cisplatin modulates adenosine A(1) receptor expression in vivo and whether these receptors play a role in the nephrotoxicity. Male Sprague-Dawley rats, treated with cisplatin (8 mg/kg), developed nephrotoxicity within 3 days, as demonstrated by increased serum creatinine and blood urea nitrogen. Cisplatin also produced a significant increase in malondialdehyde, apoptosis and necrosis in the kidney. The above changes were associated with a time-dependent increase in the expression of adenosine A(1) receptor, as determined by radioligand binding assays, Western blotting and immunocytochemistry, and an increase in adenosine A(1) receptor transcripts. Administration of selective and nonselective antagonists of the adenosine A(1) receptor produced either no change or exacerbated the nephrotoxicity produced by cisplatin. These data indicate that cisplatin can regulate the adenosine A(1) receptor in the kidney and suggest a cytoprotective role of this receptor subtype against cisplatin-induced nephrotoxicity.